Each year tens of thousands of pounds of mercury-containing wastes are discharged by dental offices into municipal waste systems. Amalgam fillings typically contain about 50% mercury by weight. Mercury is a known environmental contaminant, classified by the USEPA as a persistent, bioaccumulative, and toxic material. Waste water treatment plants must meet strict limits on the amount of mercury they can release. The discharged form of mercury is typically highly toxic (i.e., unstable) and in violation of applicable environmental regulations. Although particulate removal systems used in some dental offices remove mercury-containing particles, they do not remove dissolved mercury and mercury-containing compounds. Examples of such devices are described in U.S. Pat. Nos. 5,885,076; 5,797,742; 5,795,159; 5,577,910; 5,227,053; 4,753,632; 4,591,437; 4,385,891; and 5,114,578, all of which are incorporated herein by this reference.